1. FIELD OF THE INVENTION
The invention relates to a heat exchanger having a plurality of vertical pipes for upward passage of a first heat-exchanging medium, at least one compartment for passage of a second heat-exchanging medium through which said pipes extend, a lower chamber through which said first medium passes and into which said pipes open for admission to the pipes of said first medium and a flow distribution element adapted to distribute the flow of the first medium in the lower chamber to the pipes. A fluidizable particulate material is present which, in operation of the heat exchanger, is maintained in a fluidized state in the pipes by the flow of the first medium. The pipes have inlet elements extending downwardly into said lower chamber with their lowermost ends open. Stabilization openings are provided from the lower chamber into the inlet elements above the lowermost ends of the elements.
2. DESCRIPTION OF THE PRIOR ART
A heat exchanger of the kind described above is disclosed in published British Patent Application No. GB 1,592,232. In such a heat exchanger where the first heat exchanging medium is conducted through a mass of fluidized particulate material in a number of vertical pipes, particular care must always be taken as to the stability of the process. If preferred flows occur through one or a few of the pipes the fluidized material will expand in these pipes and move over to the other pipes via a common upper box into which all the pipes open. The mass of fluidized particles will then collapse in these other pipes so that the flow of the first heat exchanging medium will be concentrated entirely in the pipe or pipes of preferred flow. This leads to the heat exchanger operating only partially and less than optimally, and increases the likelihood of the pipe walls being dirtied.
Various measures have already been incorporated for improving the stability of the process, such as fitting the flow distribution element for the lower chamber and extending the pipes by means of the inlet elements which extend into the lower chamber. Improvement is also obtained by inserting the "stabilization openings" in the walls of these inlet elements. It should be noted, furthermore, that proposals have been made for improving the stability of the flow through the various pipes by including throttle openings at the bottom of each pipe or by impeding cross travel of the particulate material in the upper chamber into which the top ends of the pipes open.
Each of these measures can contribute towards improving stability. However, it has been found that under certain circumstances instability in the flow pattern may be the result of the blockage of one or more of the stabilization openings in the inlet elements.